The primary purpose of a safe and arm (S&A) device is to prevent accidental functioning of a main charge of explosive (military or otherwise) in a fuze prior to arming. Typically, in an electro-mechanical S&A device, a sensitive primary explosive is physically separated from a booster explosive by an interrupter or barrier component. The barrier component, often a slider or rotor, interrupts the explosive path and thus prevents detonation of the booster and main charge prior to arming. Arming occurs by moving the barrier component to align the explosive elements. In the case of an electrical S&A device, the detonator includes a firing capacitor. In order to place the S&A device in a safe condition, the firing capacitor's charge is discharged, thereby preventing any energy from reaching the detonator.
In many applications, the S&A device functions to prevent arming of the fuze until a pre-programmed or designed sequence of environmental events have been sensed and compared. Once this sequence of events has been sensed, the S&A device operates to remove the safety features and progress into the armed condition by, for example, aligning the elements of the firing train.
To assure maximum safety for the user of today's modern munition systems, one environmental event the S&A device may require to allow movement from a safe to an armed condition is a safe separation distance between the source of the munition (such as a launcher) and the munition's warhead. Due to the high “g” maneuvering ability of today's munitions, it is possible that an armed munition could re-enter the launcher's safe separation envelope due to the combined vectors of the launcher, the target, and the munition, which is tracking the target, or is being directed by a different method (AWACS, laser designator, etc.). This safe separation envelope between the launcher and the launched munition precludes inadvertent blast and/or fragmentation damage to the launch platform. Therefore, there is a need for a method of continually controlling the operation of a S&A device according to the requirement of a safe separation envelope between a launcher and a munition.